LinkedIn has proven to be one of the most powerful tools for SaaS conversions. The trick is to connect and build good rapport before pitching your product. It is one of the most powerful tools to onboard new users.
I think it is, if it's a B2B facing product. If your product is for B2C, then no. People are browsing LinkedIn mainly to help improve their careers and business. If your product can solve a pinpoint for their business, then LinkedIn can be quite good.